Drug delivery devices for administering liquid medicaments are widely known in the art. Parenteral administering of liquid medicaments is typically conducted by means of injection devices, such like syringes, pen-type injectors or by means of infusion pumps, e.g. by way of micropumps.
For treatment of chronic diseases, such like diabetes the medicament has to be regularly administered according to a predefined schedule. Known drug delivery devices may either be adapted for discrete use for injecting of a predefined amount of the medicament a given number of times during the day. Alternatively, such drug delivery devices may be adapted for continuous or quasi-continuous delivery of the medicament through a permanent fluid connection between the delivery device and the patient. Continuous or constant administering of the medicament is typically conducted by means of infusion pumps that are relatively expensive.
Such drug delivery devices typically comprise a reservoir to accommodate the liquid medicament and having an outlet in fluid communication with some kind of infusion or injection needle. Moreover, such drug delivery devices also comprise a drive mechanism that is operable to expel or to withdraw a predefined amount of the liquid medicament from the reservoir and through the infusion or injection needle into biological tissue of the patient.
There exist reusable as well as disposable devices, wherein with reusable devices the medicament-containing reservoir or container is to be replaced when empty. With disposable drug delivery devices a pre-filled reservoir is non-detachably arranged in the device. When the medicament contained therein has been used up the entire device is intended to be discarded.
Traditionally, vitreous or glass cartridges have been widely used in injection or infusion systems to contain or to accommodate the liquid medicament, hence a particular pharmaceutical composition. Glass cartridges, vials or carpules provide a large degree of optical transparency and are substantially inert to the medicament. This means, that substantially no interaction between the medicament and the glass cartridge takes place even under long term storage conditions, i.e. when the medicament is stored and contained in the cartridge for time intervals of severely years.
Vitreous cartridges or glass cartridges are prone to mechanical impact and may therefore represent a concern for patients but as well for the pharmaceutical industry. Glass breakage typically represents a hazard for the patient as well as for the industrial production environment. Moreover, handling of broken glass is quite risky and dangerous for the persons concerned with a broken cartridge.
Especially with highly concentrated medicaments and with infusion pump applications comparatively small volumes have to be injected or low volume flow rates have to be realized. Extraction and withdrawal of a comparatively small amount of medicament from a vitreous cartridge may be rather elaborate since a piston typically sealing a proximal end of the cartridge is to be displaced in distal, hence in injection direction typically by means of a plunger of the drug delivery device. For such application scenarios use of a deformable or flexible container or reservoir would be advantageous. As the medicament is sucked or withdrawn from the interior of the container the container is subject to a modification of its geometric shape and may start to collapse.
Containers filled with a liquid medicament are typically pierced or punctured by a cannula or a similar piercing element by way of which the liquid content of the container can be withdrawn therefrom. With many injection devices or drug delivery devices access to the interior of a flexible container is obtained by means of a piercing assembly, wherein a piercing element, such like a cannula or injection needle is displaceable relative to the injection device and relative to the flexible container in order to pierce a sidewall or a seal thereof. Reservoirs and containers to be used with infusion or injection devices may be flexible so as to facilitate a complete emptying of the container or reservoir. A container or reservoir with a flexible structure is of particular use when the medicament located therein is withdrawn by way of suction. The withdrawal of the medicament is then accompanied by a deformation or shrinking of the inner and outer dimensions of the respective container or its wall structure. As the sidewalls of a flexible container collapse or shrink they may block a fluid outlet thereby preventing a complete emptying of the container.